
Korythalia |

Not a lot. Most Shelyn specific magic items are not combat oriented. Unless your helm has a special ability like wild, that is off the list. You should only have the stats of a raven, so one bite attack. If you have a hair attack, such as the prehensile hair hex, you should still have access to that in animal form as long as it doesn't require verbal or somantic compoments.

Paladin of Baha-who? |

Any polymorph effect eliminates any attacks you have and replaces them with the natural attacks of the form you shift into.
As a GM, I wouldn't consider your hair to work in raven form, but then I also wouldn't let a Tengu take the prehensile hair hex or the white-haired witch archetype in the first place, since they don't have hair. It's not entirely clear whether, according to a strict reading of the rules, an individual with no hair of any sort can make use of such abilities.

graystone |

Ah... I think your main attack is to give heartburn to whatever eats you. :)
The actual answer is you have one d3 bite with no reach. As paladin said, you don't have hair as a raven so there is nothing to control. "a white-haired witch gains the ability to use her hair as a weapon." No hair, no weapon.
Avians only have Armor, belt, chest, eyes, headband, neck, ring and wrist magic slots (animal archive), so head items like the helm are absorbed.
You lose your natural attacks and gain the forms natural attacks.
That just leaved you with the ravens bite.

lemeres |

Generally, you lose all your normal natural attacks and gains the natural attacks of the form you gain.
There are some exceptions though. The transmutation school does include lines about how certain abilities that add on natural attacks after the fact (it directly references sorcerers that might have bloodlines that grow claws) can still do so.
Not entirely sure whether the hair and gore addded after the fact though.

graystone |

I would argue that the feathers take the place of hair for a bird, especially if it's something like the Shelyn holy symbol or bird of paradise with long soft feathers
I'd say that would be an ok houserule. This is the rules section though and feathers aren't hair.
For example, the spell Winter Feathers causes "The target’s feathers thicken and fluff up to ward against winter’s chill." It does nothing for mammals, lizards and constructs as they don't have feathers.
Now, take this spell, Chameleon Scales: It actually allows you to "alter the color of your skin, hide, or scales" and doesn't limit it to JUST scales.

Korythalia |

I can see that, but I think we are already in house rule territory as the tengu is already in play. I'd also suggest that the ring in question is not combat oriented and would be a good way to get the tengu killed. The ring's power is defensive: flight to escape, change form to sneak around or spy. If your GM allows you to use your feathers as hair in combat, you're a tiny creature so your damage die is 1d2 plus intelligence mod due to size, and you can't cast spells (am I understanding this archetype correctly? Hexes are traded for hair stuff but it's still a full caster?)

Korythalia |

Graystine, as you pointed out that a tengu has no hair. So if a tengu character is using feathers in place of hair for hair based abilities and a GM has permitted this, I think that would be a house rule. If the character is in play, he is in house rule territory.
Unless by "the tengu" you thought I meant the race, that was not my intention. He's "the tengu" because I don't know his name.

graystone |

Graystine, as you pointed out that a tengu has no hair. So if a tengu character is using feathers in place of hair for hair based abilities and a GM has permitted this, I think that would be a house rule. If the character is in play, he is in house rule territory.
Unless by "the tengu" you thought I meant the race, that was not my intention. He's "the tengu" because I don't know his name.
Ok, that makes sense then. The way you had it worded it had sounded that the race was houseruled.
Taking this post into account, I'd STILL have the same reply though since this is the rules section. They don't allow feathers to be used instead of hair. If this isn't a hypothetical character, then the best bet would be to beg the DM to further houserule the feathers in the bird form to work as hair.